The general aim of the proposed research is to obtain information about the rates of formation and decay of the intermediate photoproducts formed during the photolysis of cone visual pigments and the kinetics of cone pigment bleaching and regeneration. The long range goal of this work is to arrive at a clearer understanding of the role of visual pigments and their photochemical intermediates in the generation of neural signals in photoreceptors. Previous studies on the properties of the early receptor potential (ERP) clearly show that it is closely related to the early photochemical changes in visual pigments during bleaching, and as such, provides a valuable tool to investigate the properties of the bleaching process. The time course and temperature dependence of ERPs recorded with intracellular electrodes from cones in the turtle retina will be analyzed to determine the rates of formation and decay of the photochemical intermediates generating these voltage changes. Secondly, an attempt will be made to record the voltage changes (photoproduct responses) produced by photoregeneration of the cone visual pigment from its intermediate products. These recordings will be made from cones isolated by retinal dissociation and maintained in culture. This technique will allow delivery of light directly to the outer segment thus avoiding the filtering effect of oil droplets on short wavelength light. If successful, this approach will provide a means of directly measuring the kinetics of formation and decay of cone pigment intermediates and the spectral characteristics of these intermediates. Finally, the ERP will be used to measure changes in pigment concentration during bleaching and regeneration which can be correlated with changes in receptor sensitivity.